As shown in FIG. 20, such prior art particulate sifters as disclosed, for example, in Patent Document 1 include a casing X1 into which particulates flow, a cylindrical net body X2 fixed inside the casing X1 and rotating blades X3 rotating inside the net body X2. In these particulate sifters, particulates which have flowed into the net body X2 as indicated by an arrow X4 are separated into particulates that can pass through the net body X2 and particulates and/or foreign substances that cannot pass through the net body X2 while being agitated by the rotating blades X3.    Patent Document 1: Japanese Patent Laid-Open Gazette No. 2001-70885